import SwiftUI
import UIKit


struct PageViewController<Page: View>: UIViewControllerRepresentable {
    var pages: [Page]
    @Binding var currentPage: Int


    func makeCoordinator() -> Coordinator {
        Coordinator(self)
    }


    func makeUIViewController(context: Context) -> UIPageViewController {
        let pageViewController = UIPageViewController(
            transitionStyle: .scroll,
            navigationOrientation: .horizontal)
        pageViewController.dataSource = context.coordinator
        pageViewController.delegate = context.coordinator


        return pageViewController
    }


    func updateUIViewController(_ pageViewController: UIPageViewController, context: Context) {
        pageViewController.setViewControllers(
            [context.coordinator.controllers[currentPage]], direction: .forward, animated: true)
    }


    class Coordinator: NSObject, UIPageViewControllerDataSource, UIPageViewControllerDelegate {
            var parent: PageViewController
            var controllers = [UIViewController]()


            init(_ pageViewController: PageViewController) {
                parent = pageViewController
                controllers = parent.pages.map { UIHostingController(rootView: $0) }
            }


            func pageViewController(
                _ pageViewController: UIPageViewController,
                viewControllerBefore viewController: UIViewController) -> UIViewController?
            {
                guard let index = controllers.firstIndex(of: viewController) else {
                    return nil
                }
                if index == 0 {
                    return controllers.last
                }
                return controllers[index - 1]
            }


            func pageViewController(
                _ pageViewController: UIPageViewController,
                viewControllerAfter viewController: UIViewController) -> UIViewController?
            {
                guard let index = controllers.firstIndex(of: viewController) else {
                    return nil
                }
                if index + 1 == controllers.count {
                    return controllers.first
                }
                return controllers[index + 1]
            }


            func pageViewController(
                _ pageViewController: UIPageViewController,
                didFinishAnimating finished: Bool,
                previousViewControllers: [UIViewController],
                transitionCompleted completed: Bool) {
                if completed,
                   let visibleViewController = pageViewController.viewControllers?.first,
                   let index = controllers.firstIndex(of: visibleViewController) {
                    parent.currentPage = index
                }
            }
        }
}
